1. Field of the Invention
The invention relates to a cooling structure of a rotary electric machine.
2. Description of Related Art
As a rotary electric machine such as an electric motor for a vehicle, a structure that includes a rotor that is fixed to a rotating shaft, and a stator that faces an outer periphery of the rotor is known. When this rotary electric motor is used, a stator coil provided in the stator may generate heat. One way to deal with this heat generation is to supply coolant (such as cooling oil) that is a cooling medium to the stator coil.
For example, Japanese Patent Application Publication No. 2001-95205 (JP 2001-95205 A) describes a rotary electric machine that includes a rotor that is fixed to a rotating shaft, and a stator that faces an outer periphery of the rotor. In the rotary electric machine, a center hole is provided in an axial direction in the center of the rotating shaft. Also, a through-hole is provided from the center hole toward the radial direction, and a tip end of a conduit through which coolant flows is inserted into the center hole. The coolant that flows into the center hole is sprayed from the through-hole toward a stator coil end and strikes the radially inside of the stator coil end, such that the stator coil end is cooled by the coolant.
With the structure described in JP 2001-95205 A, coolant that has been squirted out from the through-hole provided in the rotating shaft strikes the inner peripheral surface of the coil end. That is, coolant is only applied to a narrow area in the inner peripheral surface of the coil end. Therefore, a temperature difference between a low temperature portion and a high temperature portion of the coil end is large. Thus, there is a room for improvement in an efficient reduction of the high temperature portion. On the other hand, it is possible to provide a plurality of squirt holes for squirting coolant toward a surface other than the inner peripheral surface of the coil end. However, in this case, the number of the plurality of squirt holes increases, and the structure becomes complicated, which may lead to an increase in cost. For the above reason, it is desired that temperature variation at the coil end is suppressed by a relatively simple structure to expand the cooling area of the coil end.